If you recently visited a national park, chances are you took a ton of pictures. Now it turns out that vacation photos uploaded to websites can help researchers study patterns in nature tourism, a major source of revenue for many regions.

Travel and tourism account for about 9 percent of the world’s gross domestic product. Nature tourism at parks, beaches, and wildlife-watching spots is a “major and growing” part of global travel, the study authors write in Scientific Reports. Researchers often want to figure out how certain ecosystem features, such as temperature and biodiversity, affect visitation rates. But counting visitors in person is time-consuming and expensive.

The team turned to the photo-sharing website Flickr, which houses a staggering six billion-plus photos. Every year, users upload 40 to 50 million photos that have been tagged with location information. About 40 percent are taken in Europe, 39 percent in North America, and 13 percent in Asia.

Using the Flickr photos, the researchers estimated visitation rates for 836 sites around the world, including everything from national parks to art galleries. Then they compared those estimates to previously-gathered visitation data from those sites. The team found that “there is a reliable statistical relationship between the number of people counted and the flickr-generated estimate.”

The number of Flickr photos at certain locations also spiked when expected. For example, the site was flooded with new images of Black Rock Desert, Nevada every year during the popular Burning Man festival. And the number of photos taken in southern Vermont increased in October, when tourists typically visit to see the spectacular fall colors.

“[T]his new proxy measure of visitation can be applied almost anywhere: in developed and developing countries, data-poor and data-rich locations, urban areas and wilderness,” the authors conclude. “Wherever people are taking and uploading pictures we can use that information to indicate their visit and learn from it.” — Roberta Kwok | 18 October 2013